Abstract
The triggering threshold is one of the most important parameters for landslide early warning systems (EWSs) at the slope scale. In the present work, a velocity threshold is recommended for an early warning system of the Gapa landslide in Southwest China, which was reactivated by the impoundment of a large reservoir behind Jinping’s first dam. Based on GNSS monitoring data over the last five years, the velocity threshold is defined by a novel method, which is implemented by the forward and reverse double moving average of time series. As the landslide deformation is strongly related to the fluctuations in reservoir water levels, a crucial water level is also defined to reduce false warnings from the velocity threshold alone. In recognition of the importance of geological evolution, the evolution process of the Gapa landslide from topping to sliding is described in this study to help to understand its behavior and predict its potential trends. Moreover, based on the improved Saito’s three-stage deformation model, the warning level is set as “attention level”, because the current deformation stage of the landslide is considered to be between the initial and constant stages. At present, the early warning system mainly consists of six surface displacement monitoring sites and one water level observation site. If the daily recorded velocity in each monitoring site exceeds 4 mm/d and, meanwhile, the water level is below 1820 m above sea level (asl), a warning of likely landslide deformation accelerations will be released by relevant monitoring sites. The thresholds are always discretely exceeded on about 3% of annual monitoring days, and they are most frequently exceeded in June (especially in mid-June). The thresholds provide an efficient and effective way for judging accelerations of this landslide and are verified by the current application. The work presented provides critical insights into the development of early warning systems for reservoir-induced large-scale landslides.
Highlights
Landslides pose great threats to life and property
The results show that the displacement coefficients are more than 0.95 and the velocity coefficients can exceed 0.8, both suggesting that the other global navigation satellite system (GNSS) units have a strong similarity with the G2 unit in variations of displacement and velocity
Analysis of work velocity time series based onfor theanmoving average method was the improved applied is still limited in different deformation stages, which conducted for warning of periodic acceleration phases with a velocity threshold
Summary
Landslides pose great threats to life and property. Many large-scale landslides have been reactivated by the impoundment of large reservoirs behind high dams in southwestern China. An advancing regional warning model for rainfall-induced landslides, based on rainfall thresholds, has been proposed in a landslide-prone area in the Campania region, Italy [8]. Water level thresholds are used for reservoir-induced landslides, because these landslides’ behaviors are strongly related to reservoir impoundment and fluctuations [18,19,20] In this case, the two main landslide types are seepage-induced and buoyancyinduced, which are related to landslide geometry and materials [2]. A successful EWS at the slope scale encompasses proper early warning indicators, primarily using monitored displacement and its velocity and, sometimes, environmental quantities, such as critical water level and rainfall threshold [19,31,32].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
